HOW TO KNOW THE SEAWEEDS 



146b Thallus stipitate. Fig. 187 Latninaria (in part) 



Figure 187 



Fig. 187. Laminaria digitata (Linnaeus) Edmonson 



The lower part of a plant showing the holdfast, stipe and deeply 

 divided or lacerated, fan-shaped blade, X 0.32. 



Laminaria is a large genus of medium to small size kelps of which 

 some have narrow, ligulate blades and some, Uke L. digitata, have 

 broad, fan-shaped blades. The former will be encountered a Httle far- 

 ther along in this key. All of the species of Laminaria are character- 

 istic of cool to cold waters. On the central and northern parts of the 

 Pacific Coast they may be found in almost any rocky area, but in 

 southern California are confined to infratidal areas of cold, upwelling 

 water. On the Atlantic Coast they are largely confined to the cold 

 waters north of Cape Cod and are best developed at some depth 

 below low tide level. About fifteen species may be found in the United 

 States. (See other comments at step 150b.) 



147a Plants essentially simple, consisting of one or more entire or lobed 

 blades: branching mainly restricted to basal region although some- 

 times the blades proliferous from the flattened surfaces (Caulerpa), 

 or from the margins (Gigartina: Grateloupia) 148 



147b Plants branched in upper ports. 



160 



144 



